United States Coast Guard Title 33, Part 183 specifications are difficult to meet with existing polyurethane or polyisocyanurate foams when it comes to buoyancy after exposure to fully saturated gasoline vapor atmosphere, in reference fuel B, in reference oil No. 2, and in a 5% solution of Na3PO4.
Without being held to any one theory or mode of operation, it is believed that at least part of the issue focuses on the need to increase the thermal, hydrolytic and chemical stability of the foam, necessitating an increase in the phthalic anhydride containing polyols and a decrease in (or elimination of) the sucrose polyester polyol which is typically present in many foams so as to enable the foam to meet the ASTM E-84 test standards regarding the surface burning characteristics of building materials.